Bupropion/dextromethorphan (developmental code name AXS-05) is a combination drug of bupropion (Wellbutrin), a norepinephrine-dopamine reuptake inhibitor (NDRI) and nicotinic acetylcholine receptor (nAChR) antagonist, and dextromethorphan (DXM), a sigma-1 receptor agonist, NMDA receptor antagonist, and serotonin-norepinephrine reuptake inhibitor (SNRI), which is under development by Axsome Therapeutics for the treatment of treatment-resistant major depressive disorder (MDD) and agitation in Alzheimer's disease. Via inhibition of CYP2D6, similarly to quinidine, bupropion slows the metabolism of DXM and thereby increases its levels. As of 2017, the combination is in phase III clinical trials for the aforementioned indications.